Reverse cycle device



Nov 1, 1949. F. M. MacDOUGALL 2,436,608

REVERSE CYCLE DEV ICE Filed June 3, 1946 2 Shee'ts-Sheet l Hr TO EMF/s.

NOV 1949- F. M. M DOUGALL REVERSE CYCLE DEVICE 2 Sheets-Sheet 2 Filed June 3, 1946 coup/25.550 2 L, i u 1 Z m mm mr M r M M L m m w 5 Patented Nov. 1, 1949 asvrasa crow nnvrca Franklin M. MacDougall, Kirkwood, Mo., assignor to Alco Valve Company, University City, Mo., a corporation of Missouri Application June 3, 1946, Serial No. 874,052

1 11 Claims.

The present invention relates to a reverse cycle device. It finds typical use with reverse cycle coolers, which employ the principle that a conventional expansion type of refrigeration system absorbs heat in evaporator coils and gives up heat in condenser coils, and that it may thereby be used as a cooling means with respect to the evaporator and a heating means with respect to the condenser. Conventionally, this may be done by having a system in which the cycle may be reversed, so that a given coil in a given area may be operated selectively as either an evaporator or a condenser, while its counterpart is oppositely operated. The area may thereby either be cooled or heated.

It is an object of the invention to provide a valve mechanism, or selector valve device, that can easily perform the reversal of the refrigeration cycle, so that a particular, coil may, at one time, be a condenser and, at another time, an evaporator.

It is an object of the invention to provide a control valve for a reverse cycle system having a main valve that may be externally operated, preferably manually, to select whether heating or refrigeration is to be had, and in which the complete change-over follows from the operation of this main control valve. A further object is to provide a main control valve as aforesaid, with a follow-up type of valve to complete the reversing cycle, which follow-up valve is caused to operate by the changed conditions in the system that result from the shift of the main valve,

An object is to provide a valve of this kind having multiple valve elements ,that are conjointly operated without requirement of exacting machining of the operating parts. A further object is to employ a pressure diflference in the system to cause one valve to shift in response to the mechanical shifting of another valve.

A further object is to provide a valve substantially free of pressure drop except under conditions wherein the valve is to be shifted as aforesaid. An additional object is to provide a system wherein the mechanically operated valve may be shifted in the middle of a cycle, and the following valve will shift promptly thereafter. Specifically, it is an object to provide a system wherein the pressure difference holding the secand valve seated is quickly relieved.

A further object is to provide a four-way valve of this type, that relieves the compressor of load at the start of a cycle.

A further object is to provide a reverse cycle refrigeration system wherein the shifting of a valve eifects'reversal of the cycle, by producing complete seating of a second valve.

A further object is to provide a change-over valve construction of the foregoing type which is compact, simple in construction, easily serviced, and relatively inexpensive.

A further object is' to produce a valve mechanism that controls a short circuit line around the compressor, which valve mechanism is automatically opened when the compressor pressure is stopped, remains open at the start, and closes to cut oil the short-circuit line only after the compressor comes up'to speed, whereby the compressor may develop speed at minimum load.

Other objects will appear in the accompanying description and in the drawings.

In the drawings:

Fig. 1 is a plan view of the mechanism;

Fig. 2 isa vertical side-to-side section, taken on the line 2-2 of Fig. 1;

Fig. 3 is a horizontal side-to-side section, taken through the main valve on the line 3-3 of Fig. 2;

Fig. 4 is an end elevation, taken from the right end of Figs. 1 and 2; and 1 Fig. 5 is a diagrammatic view of a system including the valve.

Referring particularly to Fig, 5, it may be seen that this valve can be used with a conventional refrigeration system including a compressor ill, a coil II, a coil l2, and an expansion valve l3, here shown as the thermo type of valve, of the type having a separated equalizer chamber and a temperature bulb l5.

The valve of the present invention is generally indicated at Hi. It has a main inlet II, a first coil passage it, a second coil passage 19, and a compressor return outlet 20.

The compressor I0 is connected to the inlet IT by a pipe 2|. The first coil passage I8 is connected to the coil II by a pipe 22. The second coil passage I9 is connected to the coil l2 by a pipe 23. The compressor outlet 20 is connected back into the inlet side of the compressor by a pipe 24.

The coil I l is connectedwith the thermal valve l3 by a pipe 25, and the coil I2 is connected-with the thermal valve by a pipe 26. The equalizer chamber of the thermal valve is connected to the line 25 through a normally open check valve 21, and is connected to the line 26 by a normally open check valve 28. These valves are shown as gravity biased, though they may be spring biased. The requirement is that each close when the pressure on its inlet side exceeds that on its outlet side by a predetermined amount.

The valve l6 appears in Fig. 2 in a manner that shows all of its parts. There is an inlet housing 30, into which the inlet I1 connects. This inlet may be at the back, as it appears in Fig. 2, and also as is indicated in Figs. 1 and 4.

The inlet housing 30 may be stamped from a tube to the shape shown to receive the coil passage |8, which is in the form of a pipe. The pipe 3| projects into the housing and interfits with the inturned edge of the housing 30 to which it is permanently secured. The inner projecting end of the pipe 3| provides a valve seat 32.

The other end of the cup-shaped inlet member 30 receives another pipe 33. Adjacent its inner end, the pipe 33 has a union disc 34, secured thereto as by soldering, or the like. This disc 34 is adapted to interfit into a groove around the inside of the housing member 30, and is given a sharpened edge to produce a tight fit. A threaded union connector 35 fits over the disc 34 and is screwed onto the end of the housing 30, so as to hold these parts securely together. The inner end of the pipe 33 is formed into a valve seat 36 that is disposed directly opposite the valve seat 32 within the housing 30.

The outer end of the pipe 33 is plugged, as at 38, this plug being permanently sealed into the end of the pipe. This plug has an axial bore 39 extending thereinto and receiving and guiding one end of a valve stem 40. This valve stem carriw a double-faced valve head 4|. at its end within the housing 30. The head is held by being fitted over a reduced end of the valve stem 4| against a washer 42. Another washer 43 is then fitted over the other side of the valve head 4| and secured into position by a nut 44 engaging over a, threaded part of the end of the valve stem.

The valve stem is additionally guided by a guide member, generally indicated at 41. This is formed of a small piece of light tubing that just fit within the inside of the pipe 33. The central parts 48 of this piece of light tubing are stamped inwardly toward the center of the piece and are spaced apart a distance only slightly greater than the diameter of the valve stem 40, whereby the stem may be guided by them and held at a central position within the tubing.

The valve stem and its valve are positioned by a coil spring 50. This spring has its end convolutions threaded into a' socket in the end of the plug 38, and has the convolutions at its other end engaged in a groove around the valve stem. The spring 50 is a neutralizing spring tending to keep the valve head 4| at a point between the two valve seats 32 and 36.

The pipe 33, extending from the right of the housing 30, has a connector pipe 55 extending therefrom and secured into the coil passage l9, which is in the former a pipe. This pipe is secured into another housing 51 that is formed in a fashion similar to the housing 30. The pipe |9 has a union disc 58 secured adjacent its end, and this union disc is interfitted with the housing 51 and secured in position by a union connector 59. This attains a sealed joint, particularly as it is shown that the union disc 58 is provided with a sealing edge at its inner face. The inner end of the pipe I9 is' shaped to form a valve seat 60. v

The housing 51 has the outlet 28 leading therefrom, this outlet being similar to the inlet l1 coming into the housing 30. The housing 51 also receives a pipe 84 that extends into the end in the manner shown and is united thereto as by soldering. The pipe 64, at its inner end, provides a valve seat 65 that is disposed opposite the valve seat 60 on the pipe 56. The pipe 64, at its outer end, has an attachment flange 61 secured thereto, as by oldering or the like. The

I end of the pipe 64 fits into a recess in a handle block 68. Suitable screws 69 pass through the handle block and are engaged into the flange 61 to hold these two parts together, in a manner to appear.

There is a second valve 10 disposed between the two valve seats 60 and 65. This valve 10 is mounted on a valve stem H in a manner similar to the mounting of the valve 4|. It is fitted over a reduced end of the stem 1| against a washer l2, and is clamped thereon by a second washer l3 and a nut 14. A guide 15, similar to the guide 41, is provided adjacent the inner end of the tube 64 to guide the valve stem. A bellows 11 has its head sealed onto the stem II, and its other end is sealed to a cup-like ring 18 that is soldered or otherwise permanently attached in sealing relationship to the outer end of the pipe 64, with which it interfits in the manner shown. The bellows thus seal off the inside of the pipe 64.

The valve stem 1| passes into a recess within the handle block 68, wherein it has a spool member 8| permanently attached to it as by soldering. The block 68 likewise has a transverse bore that receives one end of a handle shaft 82. This handle shaft has an eccentric button 83 on its inner end, this button projecting into the recess 80 and interfitting between the flanges of the spool member 8|, so that, when the shaft 82 is oscillated, the spool member, and consequently the valve shaft II, will be moved axially within the pipe 64.

A split spring washer 85 is engaged around a neck in the handle shaft 82 land fits within a recess 86 in one face of the handle block 68. This shaft 82 may pass through a supporting panel 81. A screw 88 fits through the panel 8! and into the block to hold these parts together. A handle 90 is attached to the handle shaft 82 outside the panel 81, so as to rotate the shaft and operate the valve. This handle is provided vzith a recess 9| to receive the head of the screw 8 The pipe 64 has a connecting pipe 94 opening thereinto, that opens into the pipe 3|. These parts are Permanently attached together in sealing relationship, as by solder.

There are two brackets 96 that are generally U-shaped with their legs secured to the vertical pipes 55 and 94 in the manner shown in Fig. 4.

This attachment may be by soldering or the like. These two brackets also receive screws 91 that attach the parts and support the device on the panel 61, alon with the screw 88.

Operation It is assumed that suitable means for starting and stopping the compressor Ill are provided. These may be manual means or automatic means of any of the types well known in the art. At the time of such a start of the compressor, the valve 4| will be in its neutral position, to which it is urged by the spring 50. The valve 10 will be disposed in one or the other of its positions. As shown in Figs. 2 and 5, the valve 10 is closed against the seat 60.

At the start, the compressor will have equal discharge and suction pressures, such as 75 p. s. i.

aieaeoe It establishes a flow through the line 2| and the inlet I! to the interior of the housing 30. With the valve 4| in neutral position, this flow may divide between the two valve seats 32 and 36. However, the flow past the valve seat 321s by way of a short circuit through the pipe 34, the pipe 64, past the valve seat 65, the outlet 26, and the line 24 back to the compressor. The flow past the valve seat 36 must flow through the pipe 55, the coil passage It, the line 23, and devices in that line. This latter flow path offers a much higher resistance than does the short circuit. Consequently, there will be a very high flow through the short circuit, and a resultingly high pressure drop across the valve seat 32 compared to that across the valve seat 36. The orifice effect of the valve seat '32 is increased by the fact that, when the valve 4| is in neutral position, the flow path through the valve seat is relatively constricted. Thus a higher pressure exists on the right hand side of'the valve 4| than exists on the left hand side, and the pressure difference is suflicient to overcome the spring 60 and cause the valve 4| to shift into seating position on the valve seat 32. Thereafter, the short circuit is cut off and the full pressure of the compressor is directed against the right hand side of the valve 4|, while the compressor pulls on the left hand side of the valve. This results in a high pressure differential. that firmly seats the valve 4| on the seat 32. This holding of the valve on its seat by the pressure conditions is a valuable fea: ture in similar valve mechanisms that have different means for initially moving the valve 4|.

After the foregoing, the flow must then take place through the valve seat 36, the pipe 55, the

passage l9, the line 23, and the coil I2, and the line 26 to the thermal valve. The inlet side of the compressor is pulling down on the line 25 to the left of the thermal valve, the coil ll, theline 22, and the connections through the pipe 94 past the valve seat 65 and theline 24. Hence, the pressure is reduced on the outlet side of the thermal valve, to caus the same to open.

As the thermal valve acts as a pressure reducer, the differential pressures, acting on the valve 4 I, are continued, and it stays seated against the valve seat 32.

The thermal valve acts in its expected manner to maintain a constant superheat at the evaporator side, it being understood that, with the cycle lust described, the coil i2 acts as a condenser and the coil II as an evaporator. As will appear, the thermal valve maintains constant superheat by the response of the bulb IE to temperature at the compressor inlet side, and the response of the usual diaphragm to evaporator pressures, acting oppositely to the bulb.

The foregoing operation will continue until the compressor is shut off. When this occurs, the valve 4| will again neutralize, owing to the equalization of the pressures on its opposite sides. At the pointof shut-01f, there will be refrigerant in the coil II, which is trapped by the fact that the compressor is stopped. Also, the pressure on the right hand side of the valve 4| is reduced by stopping the compressor. The trapped gas in the coil II and associated parts will tend to increase with the decrease in compressor pressure, and this. augmented by inevitable leakages, will equalize the pressures on the opposite side of the valve 4| so that the same neutralizes under influence of the spring 50. When the compressor re-starts the cycle is repeated.

is stopped, the pressures in the system will be equalized; and, when the compressor re-starts with the valve 10 reversed, thecycle will be identical but the direction of flow reversed. In such case, the valve 4| will be caused to shift to the right, seating against the valve 36. The compressor will deliver the hot gas to the coil II, which then acts as a condenser. The liquid from the condenser will be delivered in the opposite direction to the thermal valve, which, in turn, will deliverthe refrigerant mixture to the coil l2, which now acts as --an evaporator.

The thermal valve may be of the conventional externally equalized type, wherein the pressure from the line 24 at the inlet side of the compressor is introduced below the diaphragm thereof to act in opposition to the pressure generated from the bulb l5. Such is conventional in the art. It permits the use of the thermal valve for flow in either direction.

If the valve 10 is manually shifted in the midst of an operation by the compressor, there is an additional problem in equalizing pressures on opposite sides of the valve 4|. Assume, under such circumstances, that the valve 10 is seated against the seat 60, as shown in the drawings. During a cycle, with the valve I0 so positioned, the valve 4| will be seated against the seat 32, the compressor will be delivering hot gas to the coil l2, with a return flow through the left hand side of the four-way valve. If the valve I0 is suddenly shifted to its seat 65, the compressor will be immediately short circuited, but will continue to deliver relatively high pressure to the right hand side of the valve 4|. The left hand side of this valve is at a relatively low pressure of gas, which is now trapped by the closure of both of the valves 4| and 10 to the left. With this gas.

trapped in the evaporator, its pressure will increase somewhat. The pressures acting oppositely on the valve 4| will equalize through leakage or the like. However, this leakage must take place despite the fact that, with an external equalizer, the inlet side of the compressor tends to have equal pressures with the outlet side, which means an increased pressure in the external equalizer chamber of the thermal valve that seats this valve.

The use of the check valve connection, shown in Fig. 5, for the thermal valve, increases the speed of equalization of pressure on the two opposite sides of the valve 4 It will be seen that, in place of the conventional external equalizer line, the

equalizer chamber is connected both to the lines 25 and 26 on the opposite sides of the thermal valve l3. However, there are two normally open check valves 21 and 28 in these lines. These two check valves are normally biased open by gravity or by springs, or both, in the manner of well known' check valves, to afford a necessary pressure diiferential between their inlet sides and outlet sides requisite for their closing.

At the start of any normal cycle, both of the valves 21 and 28 will be open. Consequently, the equalizing chamber of the thermal valve is open to both the lines 26 and 25. If the flow through the system is to the right with the valve I0 in its right hand position, as shown in Fig. 5, the

compressor will rapidly develop a high pressure to the right hand side of the valve 28. The left hand side of this valve will be approximately at the low pressure on the left hand side of the thermal valve. This difference of pressures is suilicient to cause the valve 28 to close. When it If the valve IO-is reversed when the compressor closes, the valve 21 will have substantially equal aesaeos pressures on its oppositesides, so that it will remain open and there will result the equivalent of internal equalization of the thermal valve by the connection of the equalization chamber the outlet side of the thermal valve. The reverse flow cycle is operable in a'similar mannerin that the valve l'l will close and the valve 28 will open when 25 is the inlet linetothe thermal valve and 2 6 the outlet line.

' With the check valves 21 and 28, as shown, a shifting of the manual valve 10, when the compressor is in operation, will be followed by rapid equalization of pressures on the opposite side of the valve 4|. If it be assumed that the valve 10, during the start of any cycle of operation, is in the position shown in Fig. 5, and the valve II is seated to the left against the valve seat 32, there will be ahigh pressure to the right of the thermal valve in the line 26 and a lower pressure to the left of the thermal valve in the line 25, the coil II and associated parts. A shifting of the valve in the midst of such a cycle will be followed by the short circuiting of the compressor and the trapping of gas at evaporator pressure on the left hand sides of the valves 4! and I0. Short circuiting of the compressor will cause a reduction of the liquid pressure on the right hand side of the thermal valve, whereas the trapping of the gas in the evaporator will cause an increase in pressure on the left hand side of the thermal valve. The valve 21 is already open, and, as a result of the converging of the two pressures acting oppositely on the valve 28, it will be caused to open when the pressure differential acting on it declines to a value below the predetermined value. Consequently, the valve 28 will very shortly open, and there will be a continuous pressure line from one side to the other of the valve 4|, which will thereupon neutralize under the infiuence of the spring 50.

It will be seen that, with this arrangement, the valve 4| returns to neutral for each cycle- As a result, the compressor starts substantially unloaded, because it is short circuited at the start. It thereby requires less starting torque of the compressor motor to bring it up to speed. This is a valuable feature in connection with thereverse cycle system, but it also has value in systems wherein flow is unidirectional.

There is no substantial pressure drop through the four-way valve, except when it is in a short-v circuited condition. In other words, the passages and valve ports are all of sufiicient size to permit the flow to take place with no substantial pressure drop, except when the valve 4| is in neutral position and the compressor is short circuited. At such short-circuited operation, there is very much increased flow around the compressor, and this increases the pressure drop across the valve 4i, causing it to seat promptly. When the cycle is in its operating condition, there is a much smaller flow, and consequently any pressure drop across the valve seat 36 is, for all practical purposes, discounted. Also, when the valve 4| is moved to a seated position, the opening for its opposite valve seat is sufiiciently large to permit flow to take place without the substantial pressure drop.

It is also evident that the two valves in this application are caused to operate substantially in unison, but without the necessity of mechanical connection that seats both valves at the same time. Such mechanical connections always offer difficulties, because they require very accurate machining of parts, and, even so, frequently are unsatisfactory because of the radically different temperature conditions that exist around the present valve is independent "pressure outlet from the first valve chamber, a

high pressure fluid inlet to the second valve chamber, a first work passage from the first and third valve seats, a second work passage from the second and fourth valve seats, a first valve movable between the first and second valve seats, a second valve movable between the third and fourth valve seats, means to move the first valve to connect the first work passage to the outlet, and means to cause the second valve to move to connect the second work passage to the inlet when the first work passage is connected with the outlet, said first and second means providing independent movement in the operation of the two valves.

2. A control for reverse cycle fluid flow systems, including two valve chambers, first and second valve seats in the first chamber, third and fourth valve seats in the second chamber, a low fluid pressure outlet from the first valve chamber, a high pressure fluid inlet to the second valve chamber, a first work passage from the first and third valve seats, a second work passage from the second and fourth valve seats, a first valve movable between the first and second valve seats, a second valve movable between the third and fourth valve seats, means to move the first valve to connect the first work passage to the outlet, and means to cause the second valve to move to connect the second work passage to the inlet, said last named means including pressure-responsive means causing the second valve to shift by reduction in pressure on its side open to the outlet, caused by disposition of the first valve to connect the first work passage with the outlet, said first and second means providing independent movement in the operation of the two valves.

3. A'control for reverse cycle fluid flow systems,

including two valve chambers, first and second valve seats in the first chamber, third and fourth valve seat in the second chamber, a low fluid pressure outlet from the first valve chamber, a high pressure fluid inlet to the second valve chamber, a first work passage from the first and third valve seats, a second work passage from the second and fourth valve seats, a first valve movable between the first and second valve seats, means to-move the first valve to connect the first work passage to the outlet, means to cause the second valve to move to connect the second work passage to the inlet, said last named means including pressure-responsive means causing'the second valve to shift by reduction in pressure on its side open to the outlet, caused by disposition of the flrst valve to connect the first work passage with the outlet, said first and second means providing independent movement in the operation of the two valves, and yieldable means urging the second valve to open position when fluid flow stops.

4. A control for reverse cycle fluid flow systems, including two valve chambers, first and second valve seats in the first chamber, third and fourth valve seats in the second chamber, a low fluid pressure outlet from the first valve chamber, a high pressure fluid inlet to the second valve chamber. a first work passage from'the first and third valve seats, a second work passage from the second and fourth valve seatspaflrst valve movable between the first and second valve seats, a second valve movable between the third and fourth valve seats, manual meansto shift the first valve between its seats selectively to connect the first or second work passages to the outlet, and means to cause the second valve to move to the third valve seat when the first valve closes the second valve seat, and to cause the second valve to move to the fourth valve seat when the first valve closes the first valve seat, said last named means providing movement of the second valve independent of the manual means.

5. In a valve mechanism for use with a fluid flow system having a fluid circulator, and work apparatus oflering resistance to fluid flow, a passage connectable from the circulator to receive high pressure fluid, a passage connectable into the circulator to return fluid at lower pressure, a passage connectable into the work, a passage connectable from thework, the line to the circulator being selectively connectable with the work passages, the line from the circulator being also connectable with the work passages, a valve between the circulator outlet line and the work passages disposed to open both work passages to said line, and oppositely movable to close either work passage from the line from the circulator, the faces of the valve being subjected to fluid flow of high pressure fluid from the circulator being in the flow paths thereof, means to selectively open one work passage to the low pressure circulator inlet passage, and to close the other work passage therefrom, whereby, when the valve is open with reits open side and low pressure on its closed side.

that holds the same closed. J

7. In a valve mechanism for use with a fluid flow system having'a fluid circulator, and work apparatus oflering resistance to fluid flow, a passage connectable from the circulator to receive high pressure fluid, a passage connectable into the circulator to return fluid at lower pressure,

a passage connectable into the work, a passage spect to both passages, there will result a direct flow through one side of the valve from the high pressure circulator outlet to the low pressure circulator inlet, the valve opening being such as to produce a pressure drop on the face of the valve toward said circulator inlet, and the valve will thereby be influenced to close to out oi? the direct flow from the circulator outlet to the circulator inlet.-

6. In a valve mechanism for use with a fluid flow system having a fluid circulator, and work apparatus ofiering resistance to fluid flow, a passage connectable from the circulator to receive high pressure fluid, a passage connectable into the circulator to return fluid at lower pressure, a passage connectable into the work, a passage connectable from the work, the line to the circulator being selectively connectable with the work passages, the line from the circulator being also connectable with the work passages, a valve between the circulator outlet line and the work passages disposed to open both work passages to said line, and oppositelymovable to close either work passage from the line from the circulator, the faces of the valve being subjected to fluid flow of high pressure fluid from the circulator bein in the flow paths thereof, means to selectively open one work passage to the low pressure circulator inlet passage, and to close the other work passage therefrom, whereby, when the valve is open with respect to both passages, there will result a direct flow through one side of the valve from the high pressure circulator outlet to the low pressure circulator inlet, the valve being closable selectively to cut off the high pressure inlet passage from the work passage opened to the low pressure circulator passage and to permit connection of the high pressure inlet passage to the other work line, the connections being such that the valve is then subjected to high pressure on connectable from the work, the line to the circulator being selectively connectable with the work passages, the line from the circulator being also connectable with the work passages, a valve between the circulator outlet line and the work passages, oppositely movable to close either work passage from the line from the circulator, the faces of the valve being subjected to fluid flow of high pressure fluid from the circulator being in the flow paths thereof, means to selectively open one work passage to the low pressure circulator inlet passage, and to close the other work passage therefrom, whereby, when the valve is open with respect to both passages, there will result a direct flow through one side of the valve from the high pressure circulator outlet to the low pressure circulator inlet. the valve opening being such as to produce a pressure drop on the face of the valve toward said circulator inlet, and the valve will thereby be closed to cut off the direct flow from the circulator outlet to the circulator inlet, and means normally yieldably urging the valve into neutral position wherein both work passages are open to the circulator outlet.

8. In a valve mechanism, a pair of valve chambers, a first and a second passage leading into the first chamber, a third and a fourth passage leading into the second chamber, the first and third passages being connected, and the second and fourth passages being connected, each pair of passages in each chamber having opposed valve seats, an inlet into the first chamber, an outlet from the second chamber, a first valve in the first valve chamber movable between the first and second valve seats, a second valve in the second valve chamber movable between the third and fourth valve seats, means including a displaceable actuating member connected with one of the valves tomove it from one seat to the other, and means to cause the other valve to follow the movement of the valve first moved from one of its seats to the other, said means providing an independent movement of the said other valve relative to the one first moved.

9. In a valve mechanism, a housing including a valve chamber, first and second passages connecting thereinto, said passages having a pair of valve seats disposed one opposite the other, a poppet valve movable between t he valve seats, a fluid line connected into the chamber, the valve being adapted to determine which passage is connected with the fluid line, spring means normally maintaining the valve between the seats, the spring being designed to yield the valve to movement in response to differences in fluid pressure between the inlet and the first passage and the inlet and the second passage, the spring being connected between the valve and thehoniing, one connection being by engagement of an end convolution of the spring with a groove in the part to whichit is attached.

10. A control for reverse cycle fluid flow systems, comprising two valve chambers, first and second valve seats in the first chamber, third and fourth valve seats in the second chamber, a fluid outlet from the first valve chamber, a fluid 11 inlet to the second valve chamber. a first work passage between the first and third valve seats, a second work passage between the second and fourth valve seats, a firstjvalve movablebetween the first andsecond valve seats, a secondlvalve movable between thethird and fourth valve seats, yieldable means urging the second valveto an inoperative position between the third and fourth valve seats, and manual means to selectively move the first valve to either the first or second'valv'e seat." f

11. In a valve mechanism. a pair of valve chambers, an outlet from the first chamber, an inlet to the second chamber, a first and second passage leading into the first chamber. a third and fourth passage leading 'intothe second chamber, each pair of passages in each chamber having opposed valve seats, the first and third passages being connected; and the second and fourth passages being connected, a first valve in the first, 2o chamber movable between the first and second valve seats. a second valve in the second chamber movable between the third andi'ourth valve seats. yieldable means, urging the second valve to an inoperative position between the third and fourth valve seats, and manual means to selectively move the first valve to either, the first or second valve seat.

FRANKIJN M. mcnoUG'ALL. REFERENCES CITED 'Zlhe following references are oi record in the file of this patent:

STATES PATENTS Number Name Date 2,145,575 Zwickl Jan. 31, 1939 1 FOREIGN PATENTS Number Country Date 273,126 Great Britain June 30, 1927 543,894 Great Britain Mar. 18, 1942 

